28218809 has 2 divisors, whose sum is σ = 28218810. Its totient is φ = 28218808.

The previous prime is 28218791. The next prime is 28218811. The reversal of 28218809 is 90881282.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27008809 + 1210000 = 5197^2 + 1100^2 .

It is a cyclic number.

It is not a de Polignac number, because 28218809 - 2¹⁶ = 28153273 is a prime.

Together with 28218811, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (28218889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14109404 + 14109405.

It is an arithmetic number, because the mean of its divisors is an integer number (14109405).

Almost surely, 2^28218809 is an apocalyptic number.

It is an amenable number.

28218809 is a deficient number, since it is larger than the sum of its proper divisors (1).

28218809 is an equidigital number, since it uses as much as digits as its factorization.

28218809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18432, while the sum is 38.

The square root of 28218809 is about 5312.1378935415. The cubic root of 28218809 is about 304.4478373191.

It can be divided in two parts, 282 and 18809, that added together give a palindrome (19091).

The spelling of 28218809 in words is "twenty-eight million, two hundred eighteen thousand, eight hundred nine".